FIELD OF THE INVENTION
The invention is in the field of electro-optical structures for optical systems. In particular, the invention pertains to an electro-optical module having an electro-optical component and having a receptacle for an optical fiber plug, which are arranged on a single surface of a substrate, and having a lens arranged in the optical path between the component and the receptacle.
Such modules are utilized in the transmission of signals by means of optical fibers, and contain at least one component which comprises an electro-optical transducer. An electro-optical transducer serves to convert optical signals into electrical signals and/or, conversely, to convert electrical signals into optical signals.
A module of the above-mentioned type has become known from U.S. Pat. No. 5,337,398 (European EP 0 600 645 Al) to Benzoni et al. That module comprises two electro-optical components (laser diode and photodiode) which are positioned on metal surfaces (pads) precisely placed on a silicon substrate by means of a reheatable solder. When the solder is subsequently reheated (i.e., reflow), the components are centered with respect to the pads because of the surface tension of the liquefied solder.
A multiplicity of alignment depressions are produced in the silicon material by etching into the surroundings of the pads, and thus in the surroundings of the electro-optical components. It is possible to insert into the depressions aligning elements--for example, aligning balls--which cooperate with corresponding aligning depressions in a separate carrier which is to be aligned precisely via the respective electro-optical component.
The carrier can carry a lens provided in the beam path between the component and a receptacle for an optical fiber plug, or can align the receptacle directly with respect to the components.
If the individual parts are produced with extreme precision, in particular the carrier, the bipartite aligning depressions and, if appropriate, the lens and/or the receptacle for the optical fiber plug, then the prior art module renders it possible to dispense with an active adjustment of the receptacle with respect to the electro-optical component. The height of the carrier and, if applicable, the lens diameter are, however, design variables, which exert a considerable influence on the relative position of the receptacle and/or of the optical fiber plug with respect to the electro-optical component in the Z-direction. The Z-direction is the orientation of the optical fiber or the direction of the beam path. The direct fastening, addressed in U.S. Pat. No. 5,337,398 (EP 0 600 645 Al), of the receptacle on the substrate surface can then lead to component strains when the geometry of the carrier and, if applicable, of the lens does not permit the actual positioning of the receptacle in the Z-direction to be connected directly without strain to the substrate.